How can I redirect to login page on 401 response in Angular 5?

Here is for Angular 11

import {
  HttpErrorResponse,
  HttpEvent,
  HttpHandler,
  HttpInterceptor,
  HttpRequest,
} from "@angular/common/http";
import { Injectable } from "@angular/core";
import { Observable, throwError } from "rxjs";
import { catchError, map } from "rxjs/operators";
import HttpStatusCode from "src/app/models/enums/HttpStatusCode";
import { AuthenticationService } from "./authentication.service";

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor(private authenticationService: AuthenticationService) {}

  intercept(
    request: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {
    return next.handle(request).pipe(
      map((event: HttpEvent<any>) => {
        return event;
      }),
      catchError(
        (
          httpErrorResponse: HttpErrorResponse,
          _: Observable<HttpEvent<any>>
        ) => {
          if (httpErrorResponse.status === HttpStatusCode.UNAUTHORIZED) {
            this.authenticationService.redirectToLogin();
          }
          return throwError(httpErrorResponse);
        }
      )
    );
  }
}

The following method declared in AuthenticationService

public redirectToLogin(path: string, queryParams: any) {
    this.router.navigate([path], {
        queryParams,
        queryParamsHandling: "merge",
    });
}

I resolved my problem changing my interceptor like following:

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

  constructor() {

  }
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    let accessToken = sessionStorage.getItem("access_token");
    if(accessToken)
    {
        request = request.clone({
        setHeaders: {
            Authorization: `Bearer ${accessToken}`
        }
        });
    }

    return next.handle(request).do((event: HttpEvent<any>) => {
      if (event instanceof HttpResponse) {
      }
    }, (err: any) => {
      if (err instanceof HttpErrorResponse) {
        if (err.status === 401) {
            this.router.navigate(['login']);
        }
      }
    });
  }
}

I found the solution there: https://medium.com/@ryanchenkie_40935/angular-authentication-using-the-http-client-and-http-interceptors-2f9d1540eb8

Only to support new readers, notice that in angular 7 you should use pipe() instead of do() or catch():

return next.handle(request).pipe(catchError(err => {
    if (err.status === 401) {
        MyComponent.logout();
    }
    const error = err.error.message || err.statusText;
        return throwError(error);
}));